/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package jacky.lanlan.song.extension.struts.util;

import java.lang.reflect.*;
import java.util.Arrays;

/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 *
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @author Jacky.Song
 * @since 1.2.2
 */
public abstract class ReflectionUtils {

	/**
	 * Attempt to find a {@link Field field} on the supplied {@link Class} with
	 * the supplied <code>name</code> and {@link Class type}. Searches all
	 * superclasses up to {@link Object}.
	 * @param clazz the class to introspect
	 * @param name the name of the field
	 * @param type the type of the field
	 * @return the corresponding Field object, or <code>null</code> if not found
	 * @throws IllegalArgumentException if the class or field type is
	 * <code>null</code> or if the field name is <em>empty</em>
	 */
	public static Field findField(final Class<?> clazz, final String name, final Class<?> type) {
		Assert.notNull(clazz, "The 'class to introspect' supplied to findField() can not be null.");
		Assert.hasText(name, "The field name supplied to findField() can not be empty.");
		Assert.notNull(type, "The field type supplied to findField() can not be null.");
		Class<?> searchType = clazz;
		while (!Object.class.equals(searchType) && searchType != null) {
			final Field[] fields = searchType.getDeclaredFields();
			for (int i = 0; i < fields.length; i++) {
				Field field = fields[i];
				if (name.equals(field.getName()) && type.equals(field.getType())) {
					return field;
				}
			}
			searchType = searchType.getSuperclass();
		}
		return null;
	}

	/**
	 * Attempt to find a {@link Method} on the supplied class with the supplied name
	 * and parameter types. Searches all superclasses up to <code>Object</code>.
	 * <p>Returns <code>null</code> if no {@link Method} can be found.
	 * @param clazz the class to introspect
	 * @param name the name of the method
	 * @param paramTypes the parameter types of the method
	 * @return the Method object, or <code>null</code> if none found
	 */
	public static Method findMethod(Class<?> clazz, String name, Class<?>[] paramTypes) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(name, "Method name must not be null");
		Class<?> searchType = clazz;
		while (!Object.class.equals(searchType) && searchType != null) {
			Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
			for (int i = 0; i < methods.length; i++) {
				Method method = methods[i];
				if (name.equals(method.getName()) && Arrays.equals(paramTypes, method.getParameterTypes())) {
					return method;
				}
			}
			searchType = searchType.getSuperclass();
		}
		return null;
	}

	/**
	 * Invoke the specified {@link Method} against the supplied target object
	 * with the supplied arguments. The target object can be <code>null</code>
	 * when invoking a static {@link Method}.
	 * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
	 * @param method the method to invoke
	 * @param target the target object to invoke the method on
	 * @param args the invocation arguments (may be <code>null</code>)
	 * @return the invocation result, if any
	 * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
	 */
	public static Object invokeMethod(Method method, Object target, Object[] args) {
		try {
			return method.invoke(target, args);
		}
		catch (IllegalAccessException ex) {
			handleReflectionException(ex);
			throw new IllegalStateException(
					"Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
		}
		catch (InvocationTargetException ex) {
			handleReflectionException(ex);
			throw new IllegalStateException(
					"Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
		}
	}

	/**
	 * Handle the given reflection exception. Should only be called if
	 * no checked exception is expected to be thrown by the target method.
	 * <p>Throws the underlying RuntimeException or Error in case of an
	 * InvocationTargetException with such a root cause. Throws an
	 * IllegalStateException with an appropriate message else.
	 * @param ex the reflection exception to handle
	 */
	public static void handleReflectionException(Exception ex) {
		if (ex instanceof NoSuchMethodException) {
			throw new IllegalStateException("Method not found: " + ex.getMessage());
		}
		if (ex instanceof IllegalAccessException) {
			throw new IllegalStateException("Could not access method: " + ex.getMessage());
		}
		if (ex instanceof InvocationTargetException) {
			handleInvocationTargetException((InvocationTargetException) ex);
		}
		throw new IllegalStateException(
				"Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
	}

	/**
	 * Handle the given invocation target exception. Should only be called if
	 * no checked exception is expected to be thrown by the target method.
	 * <p>Throws the underlying RuntimeException or Error in case of such
	 * a root cause. Throws an IllegalStateException else.
	 * @param ex the invocation target exception to handle
	 */
	public static void handleInvocationTargetException(InvocationTargetException ex) {
		if (ex.getTargetException() instanceof RuntimeException) {
			throw (RuntimeException) ex.getTargetException();
		}
		if (ex.getTargetException() instanceof Error) {
			throw (Error) ex.getTargetException();
		}
		throw new IllegalStateException(
				"Unexpected exception thrown by method - " + ex.getTargetException().getClass().getName() +
				": " + ex.getTargetException().getMessage());
	}

	/**
	 * Rethrow the given {@link Throwable exception}, which is presumably the
	 * <em>target exception</em> of an {@link InvocationTargetException}.
	 * Should only be called if no checked exception is expected to be thrown by
	 * the target method.
	 * <p> Rethrows the underlying exception cast to an {@link Exception} or
	 * {@link Error} if appropriate; otherwise, throws an
	 * {@link IllegalStateException}.
	 * @param ex the exception to rethrow
	 * @throws Exception the rethrown exception (in case of a checked exception)
	 */
	public static void rethrowException(Throwable ex) throws Exception {
		if (ex instanceof Exception) {
			throw (Exception) ex;
		}
		if (ex instanceof Error) {
			throw (Error) ex;
		}
		throw new IllegalStateException(
				"Unexpected exception thrown by method - " + ex.getClass().getName() + ": " + ex.getMessage());
	}

	/**
	 * Determine whether the given method explicitly declares the given exception
	 * or one of its superclasses, which means that an exception of that type
	 * can be propagated as-is within a reflective invocation.
	 * @param method the declaring method
	 * @param exceptionType the exception to throw
	 * @return <code>true</code> if the exception can be thrown as-is;
	 * <code>false</code> if it needs to be wrapped
	 */
	public static boolean declaresException(Method method, Class<?> exceptionType) {
		Assert.notNull(method, "Method must not be null");
		Class<?>[] declaredExceptions = method.getExceptionTypes();
		for (int i = 0; i < declaredExceptions.length; i++) {
			Class<?> declaredException = declaredExceptions[i];
			if (declaredException.isAssignableFrom(exceptionType)) {
				return true;
			}
		}
		return false;
	}


	/**
	 * Perform the given callback operation on all matching methods of the
	 * given class and superclasses.
	 * <p>The same named method occurring on subclass and superclass will
	 * appear twice, unless excluded by a {@link MethodFilter}.
	 * @param targetClass class to start looking at
	 * @param mc the callback to invoke for each method
	 * @see #doWithMethods(Class, MethodCallback, MethodFilter)
	 */
	public static void doWithMethods(Class<?> targetClass, MethodCallback mc) throws IllegalArgumentException {
		doWithMethods(targetClass, mc, null);
	}

	/**
	 * Perform the given callback operation on all matching methods of the
	 * given class and superclasses.
	 * <p>The same named method occurring on subclass and superclass will
	 * appear twice, unless excluded by the specified {@link MethodFilter}.
	 * @param targetClass class to start looking at
	 * @param mc the callback to invoke for each method
	 * @param mf the filter that determines the methods to apply the callback to
	 */
	public static void doWithMethods(Class<?> targetClass, MethodCallback mc, MethodFilter mf)
			throws IllegalArgumentException {

		// Keep backing up the inheritance hierarchy.
		do {
			Method[] methods = targetClass.getDeclaredMethods();
			for (int i = 0; i < methods.length; i++) {
				if (mf != null && !mf.matches(methods[i])) {
					continue;
				}
				try {
					mc.doWith(methods[i]);
				}
				catch (IllegalAccessException ex) {
					throw new IllegalStateException(
							"Shouldn't be illegal to access method '" + methods[i].getName() + "': " + ex);
				}
			}
			targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null);
	}

	/**
	 * Action to take on each method.
	 */
	public static interface MethodCallback {

		/**
		 * Perform an operation using the given method.
		 * @param method the method to operate on
		 */
		void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
	}


	/**
	 * Callback optionally used to method fields to be operated on by a method callback.
	 */
	public static interface MethodFilter {

		/**
		 * JavaBean setter方法过滤器。
		 */
		MethodFilter SETTER=new MethodFilter(){
			public boolean matches(Method method) {
	  		return 
	  			PUBLIC.matches(method) && VOID.matches(method) &&
    			!Modifier.isNative(method.getModifiers()) && // 非native
    			
	  			method.getName().startsWith("set") //set开头 
	  			&& 
	  			method.getParameterTypes().length==1 ;//只有一个参数
			}
		};
		
		/**
		 * JavaBean getter方法过滤器。
		 */
		MethodFilter GETTER=new MethodFilter(){
			public boolean matches(Method method) {
  			return
	  			PUBLIC.matches(method) && NO_ARG.matches(method) && 
    			!Modifier.isNative(method.getModifiers()) && // 非native
    			
    			method.getName().startsWith("get") // get开头
    			|| 
    			method.getName().startsWith("is"); // 或者is开头(boolean型的isXXX，也是Getter)
			}
		};

		/**
		 * <code>public</code> 方法过滤器。
		 */
		MethodFilter PUBLIC=new MethodFilter(){
			public boolean matches(Method method) {
				return Modifier.isPublic(method.getModifiers());
			}
		};
		
		/**
		 * 无参数方法过滤器。
		 */
		MethodFilter NO_ARG=new MethodFilter(){
			public boolean matches(Method method) {
				return method.getParameterTypes().length==0;
			}
		};
		
		/**
		 * <code>void</code> 方法过滤器。
		 */
		MethodFilter VOID=new MethodFilter(){
			public boolean matches(Method method) {
				return method.getReturnType()==void.class;
			}
		};
		
		/**
		 * <code>MethodFilter</code> 的“反转”操作，
		 * 把指定的 <code>MethodFilter</code> 语意取反。
		 * <p>
		 * 比如：<br/>
		 * <code>NOT.doWith(VOID)</code> 会创建所有非void方法的
		 * 过滤器。
		 */
		ReturnableHandler<MethodFilter,MethodFilter> NOT =
			new ReturnableHandler<MethodFilter,MethodFilter> (){
				public MethodFilter doWith(final MethodFilter filter) {
					return new MethodFilter() {
						public boolean matches(Method method) {
							return !filter.matches(method);
						}
					};
				}
		};
		
		/**
		 * Determine whether the given method matches.
		 * @param method the method to check
		 */
		boolean matches(Method method);
	}

}
